1. Field of Invention
This invention relates to surface modified resinous articles, and processes for making same, and more particularly, to an improved method for making said articles in a continuous manner.
2. Description of Prior Art
In the aforesaid copending patent application, there is described a method of incorporating a modifier ingredient such as a UV absorber into the surface region of a resinous body such as a PVC sheet. The method includes the steps of: (1) immersing the body in a liquid such as water, and (2) contacting the immersed body with a solution of the modifier ingredient in a solvent such as methylene chloride which is immiscible with the liquid and which will swell the surface of the resin to allow the solution to enter its surface region.
In the continuous mode of practicing this process, the solution is present as a lower layer, water is the upper layer, a continuous polymer sheet article is transported through the water, and the solution is pumped from the lower layer to the upper layer and directed onto the top surface of the sheet for a predetermined contact time during which the modifier ingredient is incorporated into the contacted surface. After the solution is applied, a jet of water is directed onto the treated surface to displace any residual solution remaining thereon.
When this process is run for an extended period at room temperature, however, it is observed that a solid precipitate of UV stabilizer accumulates on the surface of the water layer. This solid material circulates through the system and tends to clog the pumping and piping equipment used for applying the solution to the resin surface, and for displacing residual solution thereon.
While suitable filters and/or skimmers may be used in the system to remove solid material floating on the surface of the water layer, such techniques require relatively costly equipment and periodic maintenance.
Accordingly, it is an object of the present invention to provide a method for preventing the accumulation of solid precipitate material on the surface of the water layer in the underwater process of the aforesaid patent application.
A more particular object herein is to provide a physical method of substantially eliminating the problem of solid formation on the surface of the water layer in such process.
A feature of the invention is the operation of the process at a temperature lower than ambient or room temperature whereat substantially no solid material is formed on the surface of the water layer.
These and other objects and features of the invention will be made apparent from the following more particular description thereof.